Escalators are used in smaller buildings where passengers need only to travel between single floors. An example being the department store where a customer may browse from floor to floor and an elevator would be impractical.
The principle utilises both counterweights and pulleys. The escalator consists of stairs, which are joined to a continuous chain. This chain is fitted around a drive wheel which is powered by an electric motor located at the uppermost point of the escalator. The downward travelling stairs act as a counterweight to the upward travelling stairs. This means that the electric motor only has to cater for the weight of the people riding the escalator and not the weight of the stairs themselves. Every stair has two wheels on either side which run on rails positioned beneath each. These rails are aligned except at the bottom and the top. At these locations the inner rail goes beneath the outer rail enabling each stair to move to the same level as the next one. Using this technique allowance is made for the stairs to fold flat, permitting people to get on and off easily.
